Voice from the Mount said “No” (5)
I believe the answer is:
neigh
'voice from the mount' is the definition.
The answer and definition can be both to do with communicating as well as being verbs in their base form.
Perhaps there's a link between them I don't understand?
'said no' is the wordplay.
'said' indicates a 'sounds like' (homophone) clue.
'no' becomes 'nay' (I've seen this before).
'nay' is a homophone of 'NEIGH'.
Can you help me to learn more?
(Other definitions for neigh that I've seen before include "beastly noise" , "one made by Bucephalus?" , "Whinnying sound" , "Comment from stallion" , "Horse's whinny" .)